If you really, really have a problem and are happy to take the glass out to sort it then either sugar soap and a nail brush or for the ultimate cleaner for difficult stuff there's a product called klingstrip. It's mainly meant as a paint stripper but is a poultice based product (alkalis in a clay base?). You layer it on, cover with plastic bags/cling film etc to keep it moist and wait from a few hours to a couple of days (depending how bad) - then wipe and wash off.I've used that to renovate an old marble fireplace and recently to clean many years of greasy filth from tile grout. Beware using such products with aluminium.

For cleaning the grout around the cooker it was effortless..trowelled on the grout lines with an old credit card, covered them with plastic, waited 24hrs - washed off to reveal white grout.